The present invention relates generally to methods and materials for active (extracellular) secretion of amino acids which are expression products of bacterial cells.
Hypersecretion of amino acids from bacterial cells is of manifest importance in the large-scale production of amino acids in industrial processes. To date, a means of constructing cells which actively excrete large amounts of an amino acid as compared to wild-type cells is not reported. Previous attempts to increase the extracellular presence of amino acids have centered on decreasing amino acid uptake by introducing mutations in, for example, phenylalanine uptake pathways. However, such techniques produce only marginal net increases in amino acid efflux by decreasing active uptake by the cell of amino acids already lost to the medium by diffusion. For purposes of the present application, hypersecretion refers to the active secretion from host cells of quantities of an amino acid greater than quantities which passively diffuse from corresponding wild-type cells.
There is a need in the art for host cells capable of secreting large amounts of an amino acid as compared to the corresponding wild-type cells in order to facilitate production of the amino acid and to relieve toxic and inhibitory effects of high intracellular levels of amino acids. The present invention provides novel bacterial cells capable of hypersecreting an amino acid.